Unicode C

Verify JWT Using HS256, HS384, or HS512

See more JSON Web Token (JWT) Examples

Demonstrates how to verify a JWT that was signed using HS256, HS384, or HS512. (HS256 is JWT's acronym for HMAC-SHA256.)

This example verifies the signature. It also does the following:

• Checks to see if the time constraints ("nbf" and "exp") are valid.
• Recovers the original JOSE header.
• Recovers the original claims JSON.

Unicode C

#include <C_CkJwtW.h>
#include <C_CkJsonObjectW.h>

void ChilkatSample(void)
    {
    BOOL success;
    HCkJwtW jwt;
    const wchar_t *token;
    BOOL sigVerified;
    int leeway;
    BOOL bTimeValid;
    const wchar_t *payload;
    HCkJsonObjectW json;
    const wchar_t *joseHeader;

    success = FALSE;

    // Demonstrates how to verify an HMAC JWT using a shared secret (password).

    // This example requires the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    jwt = CkJwtW_Create();

    token = L"eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpc3MiOiJodHRwOi8vZXhhbXBsZS5vcmciLCJzdWIiOiJKb2huIiwiYXVkIjoiaHR0cDovL2V4YW1wbGUuY29tIiwiaWF0IjoxNDYzNDMxODEyLCJuYmYiOjE0NjM0MzE4MTIsImV4cCI6MTQ2MzQzNTQxMn0.SHnMJ11qJH5pbp22YchT_9fL2HIx0koHiUHLG67_foU";

    // First verify the signature.
    // The password used to create this JWT was "secret".
    sigVerified = CkJwtW_VerifyJwt(jwt,token,L"secret");
    wprintf(L"with correct password: %d\n",sigVerified);

    // Now try with a different password:
    sigVerified = CkJwtW_VerifyJwt(jwt,token,L"secret2");
    wprintf(L"with incorrect password %d\n",sigVerified);

    // Let's see if the time constraints, if any, are valid.
    // The above JWT was created on the afternoon of 16-May-2016, with an expiration of 1 hour.
    // If the current system time is before the "nbf" time, or after the "exp" time,
    // then IsTimeValid will return false/0.
    // Also, we'll allow a leeway of 60 seconds to account for any clock skew.
    // Note: If the token has no "nbf" or "exp" claim fields, then IsTimeValid is always true.
    leeway = 60;
    bTimeValid = CkJwtW_IsTimeValid(jwt,token,leeway);
    wprintf(L"time constraints valid: %d\n",bTimeValid);

    // Now let's recover the original claims JSON (the payload).
    payload = CkJwtW_getPayload(jwt,token);
    // The payload will likely be in compact form:
    wprintf(L"%s\n",payload);

    // We can format for human viewing by loading it into Chilkat's JSON object
    // and emit.
    json = CkJsonObjectW_Create();
    success = CkJsonObjectW_Load(json,payload);
    CkJsonObjectW_putEmitCompact(json,FALSE);
    wprintf(L"%s\n",CkJsonObjectW_emit(json));

    // We can recover the original JOSE header in the same way:
    joseHeader = CkJwtW_getHeader(jwt,token);
    // The payload will likely be in compact form:
    wprintf(L"%s\n",joseHeader);

    // We can format for human viewing by loading it into Chilkat's JSON object
    // and emit.
    success = CkJsonObjectW_Load(json,joseHeader);
    CkJsonObjectW_putEmitCompact(json,FALSE);
    wprintf(L"%s\n",CkJsonObjectW_emit(json));


    CkJwtW_Dispose(jwt);
    CkJsonObjectW_Dispose(json);

    }